Crabs don't really need the sponges in their bowls... at most all they do is help with humidity (by providing more surface area for water to evaporate from - you can also help increase humidity by covering up some of your mesh top), but they block access to the water.. crabs drink by dipping their claws in the water and drinking water off their claws. They also need to store some water inside their shells and being able to get in the water is the only way they can do that, so it needs to be deep enough and big enough for them to partially submerge. You don't have to go all out, but adding a simple airstone to a water bowl can accomplish what the sponges do but without restricting access to the water (I have a waterfall set up for mine, but that's not practical in a 10g tank). They also need access to a bowl of salt water (instant ocean works fine for that, and you can mix it a gallon at a time).
Your substrate also needs to be much deeper - crabs bury themselves to molt (and most petstore crabs are , and they won't molt if they don't feel safe, you'd need at least 6 inches for small crabs, and as they grow you may need subtrate deeper than your current tank is tall.
Everything I read indicates that crabs would dig up and destroy live plants and it may not be worth the hassle of having them. I do have some moss growing in my crab vivarium (on the waterfall), but that's it, the rest is fake and honestly it's more for my appeal than anything - I know the crabs honestly don't care.
You might want to read this: http://www.hermitcrabpatch.com/Hermi...rate-a/133.htm